Vehicle display device

ABSTRACT

A vehicle display device includes a conversion block that converts, based on correction data stored in a memory, an imaging pixel value of a specific pixel portion captured on a near side of at least one of a vanishing point or a horizon line in a camera image acquired by an outside camera into a correction pixel value in accordance with outside brightness detected by a brightness sensor, and a display control block that controls a virtual image display luminance of a display image displayed by a head-up display in correspondence with the correction pixel value converted from the imaging pixel value by the conversion block.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No, PCT/JP2018/001851 filed on Jan. 23, 2018, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2017-31370 filed on Feb. 22, 2017. The entiredisclosures of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a vehicle display device for visuallydisplaying a display image as a virtual image in a visual recognitionregion in a vehicle compartment by projecting the display image onto aprojection member that transmits an outside scenery.

BACKGROUND

Conventionally, a vehicle display device may project a display imageonto a projection member using light emitted from a head-up display(HUD: Head-Up Display). In these types of vehicle display devices, thereis a concern that luminance from the outside may adversely affect thevisibility of the projected image.

SUMMARY

According to one aspect of the present disclosure, a vehicle displaydevice is provided in a vehicle mounted with an outside camera thatacquires a camera image by imaging outside scenery and a brightnesssensor that detects an outside brightness of the outside scenery, thevehicle display device is configured to project a display image onto aprojection member, which transmits the outside scenery, to display thedisplay image as a visible virtual image in a visual recognition regionin a vehicle compartment, the vehicle display device including a head-updisplay that emits light to form the display image, a memory thatstores, as correction data, a correlation of a correction pixel valuewith respect to an imaging pixel value, the correction pixel value beingconverted from the imaging pixel value forming the camera image by acorrection according to the outside brightness, a conversion block thatconverts, based on the correction data stored in the memory, the imagingpixel value of a specific pixel portion captured on a near side of atleast one of a vanishing point or a horizon line in the camera imageacquired by the outside camera into the correction pixel value inaccordance with the outside brightness detected by the brightnesssensor, and a display control block that controls a virtual imagedisplay luminance of the display image displayed by the head-up displayin correspondence with the correction pixel value converted from theimaging pixel value by the conversion block.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is an internal view showing a vehicle compartment of a hostvehicle equipped with a vehicle display device according to a firstembodiment;

FIG. 2 is a block diagram showing the vehicle display device accordingto the first embodiment,

FIG. 3 is an image diagram showing a camera image according to the firstembodiment,

FIG. 4 is a block diagram showing a configuration of an HUD according tothe first embodiment,

FIG. 5 is a front view showing a virtual image display state of adisplay image according to the first embodiment,

FIG. 6 is an image diagram showing an imaging pixel value of the cameraimage according to the first embodiment;

FIG. 7 is a flowchart showing a display control flow according to thefirst embodiment,

FIG. 8 is an image diagram showing correction data according to thefirst embodiment,

FIG. 9 is a graph showing a correlation between a display pixel valueand an initial setting value according to the first embodiment,

FIG. 10 is an image diagram showing pixel value control data accordingto the first embodiment,

FIG. 11 is a flowchart showing a display control flow according to thesecond embodiment,

FIG. 12 is an image diagram showing an imaging pixel value of a cameraimage according to the second embodiment,

FIG. 13 is a flowchart showing a display control flow according to athird embodiment,

FIG. 14 is an image diagram showing an imaging pixel value of a cameraimage according to the third embodiment;

FIG. 15 is a flowchart showing a display control flow according to afourth embodiment,

FIG. 16 is an image diagram showing an imaging pixel value of a cameraimage according to the fourth embodiment,

FIG. 17 is a flowchart showing a display control flow according to afifth embodiment,

FIG. 18 is an image diagram showing a camera image according to thefifth embodiment,

FIG. 19 is a front view showing a virtual image display state of adisplay image according to the fifth embodiment,

FIG. 20 is a flowchart showing a display control flow according to asixth embodiment,

FIG. 21 is a graph showing a correlation between a display pixel valueand an initial setting value according to the sixth embodiment,

FIG. 22 is an image diagram showing luminance value control dataaccording to the sixth embodiment,

FIG. 23 is a flowchart showing a display control flow according to aseventh embodiment,

FIG. 24A is a graph showing a correlation between a display pixel valueand an initial setting value according to the seventh embodiment, andFIG. 24B is a graph showing a correlation between a light sourceluminance value and the initial setting value according to the seventhembodiment,

FIG. 25A is an image diagram showing pixel value control data accordingto the seventh embodiment, and FIG. 25B is an image diagram showingluminance value control data according to the seventh embodiment,

FIG. 26 is a block diagram showing a vehicle display device according toa modification of FIG. 2,

FIG. 27 is an image diagram showing an imaging pixel value of a cameraimage according to a modification of FIG. 6, and

FIG. 28 is an image diagram showing correction data according to amodification of FIG. 8.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a plurality of embodiments of the present disclosure willbe described with reference to the drawings. Incidentally, the samereference numerals are assigned to the corresponding components in eachembodiment, and thus, duplicate descriptions may be omitted. When only apart of the configuration is described in each embodiment, theconfiguration of the other embodiments described above can be applied toother parts of the configuration. Further, not only the combinations ofthe configurations explicitly shown in the description of the respectiveembodiments, but also the configurations of the plurality of embodimentscan be partially combined even if the configurations are not explicitlyshown if there is no problem in the combination in particular.

First Embodiment

First, consider a reference example vehicle display device that projectsa display image onto a projection member using light emitted from ahead-up display. In this reference example, a camera image is acquiredby capturing an outside scenery as a background of the display imagewith an outside camera so that a background luminance representing theoutside brightness of the external scene can be specified. Thebackground luminance specified from the camera image as described aboveis used in the control of the virtual image display luminance fordisplaying the display image virtually by the HUD, thereby making itpossible to reduce the deterioration of the visibility of the displayimage.

However, in order to properly acquire a camera image, in general, thereis a need to perform a filtering process such as an exposure control anda gain control in accordance with the outside brightness in an outsidecamera. For that reason, in spite of day and night having differentoutside brightness, imaging pixel values forming the camera image havethe same value or a close value depending on the filtering process, as aresult of which, in the reference example device described above, thespecified background luminance may not reflect an actual outsidebrightness. This leads to a concern that a contrast defect occurs inwhich the contrast of the display image with respect to the outsidescenery is insufficient or excessive, thereby making it difficult toreduce the visibility deterioration.

In this regard, a driving support system 1 according to a firstembodiment of the present disclosure is mounted on a vehicle 2 as shownin FIGS. 1 and 2. The driving support system 1 includes a peripherymonitoring system 3, a vehicle control system 4, and a vehicle displaydevice 5. Those elements 3, 4, and 5 are connected to each other throughan in-vehicle network 6, such as a LAN (Local Area Network), forexample.

As shown in FIG. 2, the periphery monitoring system 3 includes aperiphery sensor 30 and a periphery monitoring ECU (Electronic ControlUnit) 31. The periphery sensor 30 detects, for example, other obstaclessuch as other vehicles, artificial structures, humans and animals, whichmay collide in the outside of the vehicle 2, and traffic signs such asvelocity signs and various warning signs present in the outside of thevehicle 2 (i.e., outside the vehicle compartment 2 a). The peripherysensor 30 is, for example, one or a plurality of types including atleast the outside camera 30 a, among the outside camera 30 a, the sonar,the radar, the LIDAR (Light Detection and Ranging/Laser ImagingDetection and Ranging, and the like.

In this example, an outside camera 30 a, which is generally mounted onthe vehicle 2, acquires a camera image 33 by capturing an image of apredetermined range of an outside scenery 8 existing in front of avehicle compartment 2 a in an external environment of the vehicle 2shown in FIG. 3, The outside camera 30 a is, for example, a monoculartype or a compound eye type, and is mounted on a bumper 23, an innerrearview mirror 24, or the like of the vehicle 2 shown in FIGS. 1 and 4,As a result, an imaging region Ac of the outside camera 30 a shown inFIG. 5 is set in an area of the outside scenery 8 which can be visuallyrecognized by an occupant on a driver's seat 20 through a frontwindshield 21 of the vehicle 2 in the vehicle compartment 2 a.

As shown in FIG. 6, the camera image 33 acquired by the outside camera30 a is configured by imaging pixel values Tc of multiple colors.Therefore, the imaging pixel value Tc of the present embodimentrepresents a gradation value sensed by each pixel of the outside camera30 a for each of the colors of red (R), green (G) and blue (B) in 256gradations of 0 to 255. In other words, the outside camera 30 a of thepresent embodiment generates the imaging pixel value Tc of each pixel inan RGB data format.

The periphery monitoring ECU 31 shown in FIG. 2 mainly includes amicrocomputer having a processor and memories, and is connected to theperiphery sensor 30 and the in-vehicle network 6. The peripherymonitoring ECU 31 acquires, for example, obstacle information, trafficsign information, and the like based on an output signal from theperiphery sensor 30.

The vehicle control system 4 includes a vehicle-related sensor 40, anoccupant-related sensor 41, and a vehicle control ECU 42, Thevehicle-related sensor 40 is connected to the in-vehicle network 6. Thevehicle-related sensor 40 acquires, for example, driving stateinformation, navigation information, traffic sign information, drivingenvironment information, and the like of the vehicle 2. Thevehicle-related sensor 40 is, for example, one or multiple typesincluding at least a brightness sensor 40 a among the brightness sensor40 a, a vehicle speed sensor, a rotational speed sensor, a steeringangle sensor, a fuel sensor, a water temperature sensor, a communicationdevice, and the like.

In this example, the brightness sensor 40 a, which is generally mountedon the vehicle 2, detects the illuminance or luminance of apredetermined range of the outside scenery 8 existing in front of thevehicle compartment 2 a in the outside of the vehicle 2 shown in FIGS. 1and 5, as an outside brightness Lo. The brightness sensor 40 a is, forexample, a phototransistor, a photodiode, or the like, and is mounted onan instrument panel 22, the inner rearview mirror 24, or the like of thevehicle 2 shown in FIGS. 1 and 4. As a result, a detection region Al ofthe brightness sensor 40 a shown in FIG. 5 is set in an area of theoutside scenery 8, which can be visually recognized by the occupantthrough the front windshield 21 and included in the imaging region Ac ofthe outside camera 30 a.

As shown in FIG. 2, the occupant-related sensor 41 is connected to thein-vehicle network 6. The occupant-related sensor 41 detects a state oroperation of the occupant who has been present in the vehiclecompartment 2 a of the vehicle 2. The occupant-related sensor 41 is, forexample, one or multiple types including at least a power switch 41 aamong the power switch 41 a, a display setting switch, an occupant statemonitor, a turn switch, and the like.

In this example, the power switch 41 a is operated by an occupant insideor outside the vehicle compartment 2 a to start an internal combustionengine or a motor generator of the vehicle 2, thereby detecting theoperation. The power switch 41 a includes, for example, one type ormultiple types of a rotational operation type and a push operation typeby an occupant, a remote operation type by an electronic key, and thelike.

The vehicle control ECU 42 mainly includes a microcomputer having aprocessor and memories, and is connected to the in-vehicle networks 6.The vehicle control ECU 42 includes one or plural types of an enginecontrol ECU, a motor control ECU, a brake control ECU, a steeringcontrol ECU, an integrated control ECU, and the like.

As shown in FIGS. 1, 2, and 4, the vehicle display device 5 includes anHUD 50 and an HCU (HMI (Human Machine Interface) Control Unit)) 54 fordisplaying a display image 56 as a virtual image in the vehiclecompartment 2 a.

The HUD 50 is installed in the instrument panel 22 in the vehiclecompartment 2 a, The HUD 50 forms a color display image 56 by lightemitted from a projector 51. Therefore, as shown in FIGS. 2 and 4, theprojector 51 of the present embodiment is configured by combining adisplay unit 51 a and a light source unit 51 b together. In thisexample, the display unit 51 a mainly includes, for example, a dotmatrix type TFT liquid crystal panel or the like. The display unit 51 aforms the display image 56 by driving the respective pixels inaccordance with a display pixel value Td controlled by the HCU 54. Onthe other hand, the light source unit 51 b mainly includes an LED (LightEmitting Diode), for example. The light source unit 51 b is energizedaccording to a light source luminance value Sd controlled by the HCU 54to illuminate the display unit 51 a and emit a light of the displayimage 56. With the configuration described above, a virtual imagedisplay luminance Ld of the entire display image 56 shown in FIG. 5 isdetermined by the combination of the display pixel value Td of eachpixel of the display image 56 formed in the display unit 51 a and thelight source luminance value Sd of the light source unit 51 b that emitsthe light of the display image 56 together.

The displayed image 56 formed by the projector 51 in a light emissionstate represents various information to be notified the occupant of inthe vehicle compartment 2 a. Specifically, the display image 56represents, for example, not only driving state information such asvehicle speed information and engine speed information shown in FIGS. 1and 5, but also navigation information such as route guidanceinformation and traffic congestion information, traffic sign informationsuch as speed sign information, and driving environment information suchas weather information and road surface information. In addition tothose pieces of information, the display image 56 may represent, forexample, music information, video information, mobile communicationinformation, and the like provided in the vehicle compartment 2 a.

A light beam of the display image 56 formed by the projector 51 so as torepresent predetermined information is guided by an optical system 52such as a concave mirror as shown in FIGS. 1 and 4, thereby beingprojected onto the front windshield 21 as a projection member. At thattime, the front windshield 21 made of a light transmissive glasstransmits the light beam from the outside scenery 8. As a result, thelight beam of the display image 56 reflected by the front windshield 21and the light beam from the outside scenery 8 transmitted through theshield 21 are perceived by the occupant on the driver's seat 20 in thevehicle compartment 2 a.

As described above, the display image 56 is superimposed on the outsidescenery 8 as the virtual image imaged ahead of the front windshield 21so that the display image 56 can be viewed by the occupant in a visualrecognition region 7 within the vehicle compartment 2 a. Therefore, asshown in FIG. 5, the display region Ad in which the virtual image of thedisplay image 56 is displayed is set to a range in which the occupantcan visually recognize the image through the front windshield 21, and isalso included in the imaging region Ac of the outside camera 30 a andthe detection region Al of the brightness sensor 40 a.

As shown in FIG. 2, the HCU 54 mainly includes a microcomputer having aprocessor 54 a and a memory 54 b, and is connected to the HUD 50 and thein-vehicle network 6. The HCU 54 controls the virtual image display ofthe display image 56 by the HUD 50. At that time, the HCU 54 executes adisplay control based on, for example, information acquired or detectedby the ECUs 31 and 42 and the sensors 40 and 41, and information storedin the memory 54 b. The memory 54 b of the HCU 54 and the memories ofthe other various ECUs are configured with the use of one or multiplestorage media such as, for example, a semiconductor memory, a magneticmedium, an optical medium, or the like.

In this example, the HCU 54 reads out the display image 56 stored inadvance in the memory 54 b, and controls the virtual image display stateof the display image 56 by the HUD 50. For that purpose, the HCU 54executes the display control programs stored in advance in the memory 54b by the processor 54 a, thereby functionally realizing the steps of adisplay control flow shown in FIG. 7. The display control flow isstarted in response to an on-operation of the power switch 41 a, andcompleted in response to an off-operation of the switch 41 a. S in thedisplay control flow means each step.

As shown in FIG. 7, in S101 of the display control flow, the outsidecamera 30 a captures an image of the imaging region Ac of the outsidescenery 8. As a result, in S101, as shown in FIG. 6, the camera image 33configured by the imaging pixel values Tc for the respective colors ineach pixel is acquired.

In S102, the outside brightness Lo of the outside scenery 8 is detectedby the brightness sensor 40 a. As a result, in S102, the illuminance orluminance in the detection region Al superimposed on the imaging regionAc in the outside scenery 8 is acquired as the present outsidebrightness Lo shown in FIG. 5.

In S103, the imaging pixel value Tc as a correction conversion source isdetermined for each of the colors from the imaging pixel value Tc ofeach pixel in the camera image 33 acquired in S101. More specifically,in S103, first, a multiple pixel portion obtained by imaging a portionsuperimposed on a display region Ad is selected as specific pixelportion Pc in the camera image 33 in S103 a, limited to the outsidescenery 8 on a near side (that is, on the vehicle 2 side) of at leastone of a vanishing point Hp and a horizon line HI shown in FIGS. 3 and5. At this time, in the present embodiment, a pixel area which is afixed pixel area set in advance in the multiple pixel portion continuousin the vertical and horizontal directions as shown in FIG. 3 and whichis included in the detection region Al of the brightness sensor 40 a inthe outside scenery 8 and which captures an image of a range includingthe display region Ad is selected as the specific pixel portion Pc.Next, in S103, in S103 b of FIG. 7, the imaging pixel values Tc of themultiple pixel portion forming the specific pixel portion Pc selected inS103 are averaged for each color, so that an average pixel value Tcaveas the imaging pixel value Tc, which is the correction conversionsource, is calculated for each color. At least one of the vanishingpoint Hp and the horizon line HI serving as a reference of a selectedposition of the specific pixel portion Pc for averaging the imagingpixel values Tc in S103 is extracted by image processing of the cameraimage 33 or at a fixed position corresponding to the mounting positionof the outside camera 30 a.

In S104, the average pixel value Tcave calculated in S103 as the imagingpixel value Tc for each color is converted into a correction pixel valueTr for each color as shown in FIG. 8 in accordance with the outsidebrightness Lo detected in S102. Specifically, the correction pixel valueTr represents a gradation value converted from the imaging pixel valueTc by a correction according to the outside brightness Lo in 256gradations of 0 to 255 so that an actual outside brightness Lo can bereflected regardless of a filtering process by the outside cameras 30 aor the ECU 31. Therefore, in the correction pixel value Tr according tothe present embodiment, a correlation with the imaging pixel value Tc isdefined for each color, and stored in advance in the memory 54 b ascorrection data Dr. FIG. 8 shows correction data Dr which is commonlyused for all colors in the present embodiment, in particular, becausethe correlation between the imaging pixel value Tc and the correctionpixel value Tr for each color is defined to be the same.

The correction data Dr defining the correlation of the correction pixelvalue Tr with respect to the imaging pixel value Tc in this manner isprepared in the form of a table for each predetermined outsidebrightness Lo (in an example of FIG. 8, a predetermined illuminance).However, in order to reduce a storage capacity of the memory 54 b, thecorrection data Dr between the prepared outside brightness Lo isinterpolated or extrapolated from the prepared correction data Dr of theoutside brightness Lo. In order to facilitate understanding of thedescription, FIG. 8 shows the correction data Dr indicating thecorrelation for each of the three outside brightness Lo and aninterpolation between those outside brightness, but actually, thecorrection data Dr indicating the correlation for each of the outsidebrightness Lo and the interpolation between the outside brightness Lo,which are more finely divided, are realized. The correction data Dr maybe prepared in the form of an arithmetic expression in whichinterpolation is unnecessary.

As described above, in S104, the correction pixel value Tr correspondingto the average pixel value Tcave calculated in S103 is determined foreach of the colors based on the correction data Dr corresponding to theoutside brightness Lo detected in S102.

Further, as shown in FIG. 7, in S105 subsequent to S104, the displaypixel value Td of each pixel in the display image 56 is adjusted foreach color in association with the correction pixel value Tr for eachcolor converted in S104, individually. Specifically, the display pixelvalue Td of any color is expressed by the following Expression 1 withthe use of an initial setting value Td0 of the display pixel value Tdset in advance in the display unit 51 a for each pixel of the displayimage 56, and the correction pixel value Tr for each color and a maximumvalue Trmax of the correction pixel value (in this example, 255). FIG. 9is a solid line graph illustrating the correlation between the initialsetting value Td0 and the display pixel value Td according to Expression1, where a ratio Tr/Trmax between the correction pixel value Tr and themaximum value Trmax is 0.4. Therefore, in order to determine the displaypixel value Td based on such a correlation, in the present embodiment, apixel value control data Dct according to Expression 1 is prepared inthe form of a table as shown in FIG. 10, and is stored in advance in thememory 54 b. The pixel value control data Dct may be prepared in theform of an arithmetic expression representing Expression 1.

Td=Td0×Tr/Tr max  (Expression 1)

The display pixel value Td corresponding to the correction pixel valueTr converted in S104 is determined for each of the colors in S105 basedon the pixel value control data Dct stored in the memory 54 b asdescribed above. As a result, the display unit 51 a is pixel-driven inaccordance with the determined display pixel value Td for each color,thereby controlling the virtual image display luminance Ld of thedisplay image 56. At that time, in the present embodiment, the lightsource luminance value Sd according to the light source unit 51 b ismaintained at a fixed value. Therefore, the virtual image displayluminance Ld of the display image 56 shown in FIG. 5 is controlledcorresponding to the correction pixel value Tr converted in S104 byfollowing the determined display pixel value Td for each color. S105described above is continued for a valid time of the correction; andwhen the valid time has elapsed, the process returns to S101.

From the viewpoint of the description above, in the first embodiment,the functional parts for executing the S103 b of the HCU 54 correspondto an averaging block. In addition, in the first embodiment, thefunctional part for executing S104 of the HCU 54 corresponds to aconversion block, and the functional part for executing S105 of the HCU54 corresponds to a display control block.

The operation and effects of the first embodiment described above willbe described below.

In the first embodiment, the correction pixel value Tr converted fromthe imaging pixel value Tc of the camera image 33 acquired by theoutside camera 30 a is a value corrected based on the correction data Drstored in the memory 54 b as a correlation with the imaging pixel valueTc. At that time, since the correction pixel value Tr is converted fromthe imaging pixel value Tc in accordance with the outside brightness Laof the outside scenery 8 detected by the brightness sensor 40 a, it iseasy to accurately reflect the actual outside brightness Lo. Inaddition, since the correction pixel value Tr is converted from theimaging pixel value Tc of the specific pixel portion imaging a near sideof at least one of the vanishing point Hp and the horizon line HI in thecamera image 33, the influence of sunlight from an upper side of atleast one of the vanishing point and the horizontal line can be reduced.As a result, in the display image 56 in which the virtual image displayluminance Ld is controlled corresponding to the correction pixel valueTr, a contrast defect relative to the outside scenery 8 is less likelyto occur, so that the visibility can be ensured.

Further, as in the first embodiment, in the imaging region Ac of theoutside camera 30 a including the display region Ad, the actualbackground of the display image 56 displayed as a virtual image in thedisplay region Ad by the HUD 50 is imaged as the outside scenery 8.Thus, the correction pixel value Tr and the correspondingly controlledvirtual image display luminance Ld can reflect such actual backgroundimaging pixel value Tc. At the same time, as in the first embodiment, inthe detection region Al of the brightness sensor 40 a including thedisplay region Ad, the outside brightness Lo is detected in the actualbackground of the display image 56 displayed as a virtual image in thedisplay region Ad by the HUD 50. Thus, the correction pixel value Tr andthe correspondingly controlled virtual image display luminance Ld canreflect the outside brightness La of such an actual background.Therefore, according to the reflection action as described above, thereliability of the visibility securing effect can be enhanced by makingit difficult to surely cause the contrast defect.

In the first embodiment, the correction pixel value Tr is converted fromthe average pixel value Tcave calculated by averaging the imaging pixelvalues Tc of the specific pixel portion Pc which is the multiple pixelportion in the camera image 33. According to the average pixel valueTcave of the multiple pixel portion, an error caused by a local andaccidental variation of the imaging pixel value Tc can be reduced. As aresult, since the virtual image display luminance Ld controlledcorresponding to the correction pixel value Tr is less likely to cause acontrast defect caused by such a variation error of the imaging pixelvalue Tc, the reliability of the visibility securing effect can beenhanced.

In addition, according to the first embodiment, the display pixel valueTd is adjusted so as to correspond to the correction pixel value Trwhich is converted from the imaging pixel value Tc of the specific pixelportion Pc and accurately reflects the actual outside brightness Lo.Therefore, in the display image 56, according to a virtual image displayluminance Ld determined according to the display pixel value Tdcorresponding to the correction pixel value Tr, a contrast defect thatcauses a decrease in visibility can be reduced.

Second Embodiment

A second embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 11, in S103 of a display control flowaccording to the second embodiment, imaging pixel values Tc ofrespective pixels of the multiple pixel portion forming a specific pixelportion Pc are compared with each other for each of colors in S2103 bsubsequent to S103 a. As a result, in S2103 b, as shown in FIG. 12, animaging pixel value Tc of the same value or the same range is extractedfor each of the colors from a most-pixel portion Pcm in which the numberof pixels providing the imaging pixel value Tc of the same value or thesame range is largest. In this example, FIG. 12 shows the most-pixelportion Pcm in which the number of pixels providing the imaging pixelvalue Tc of the same value is largest. On the other hand, although notillustrated, the imaging pixel value Tc within the same range means thesame range corresponding to each imaging pixel value Tc of the specificpixel portion Pc in multiple ranges that are separated from each otherin advance every time the imaging pixel value Tc increases by a setamount.

As shown in FIG. 11, in the second embodiment, S103 shifts to S2104. InS2104, the imaging pixel value Tc for each color of the most-pixelportion extracted in S2103 b is converted into a correction pixel valueTr for each color in accordance with an outside brightness Lo detectedin S102. The conversion at that time is executed according to the firstembodiment. In other words, the correction pixel value Tr correspondingto the imaging pixel value Tc of the most-pixel portion Pcm extracted inS2103 b is determined for each of the colors based on the correctiondata Dr corresponding to the outside brightness Lo detected in S102.

According to the second embodiment described above, the functional partfor executing S2103 b of the HCU 54 corresponds to an extraction block.In addition, in the second embodiment, the functional part for executingS2104 of the HCU 54 corresponds to a conversion block.

As described above, in the second embodiment, the imaging pixel valuesTc of the specific pixel portion Pc which is the multiple pixel portionin the camera image 33 are compared with each other, so that thecorrection pixel value Tr is converted from the imaging pixel value Tcof the most-pixel portion Pcm in which the number of pixels providingthe imaging pixel value Tc having the same value or within the samerange is the largest. According to the imaging pixel value Tc of themost-pixel portion Pcm, an error due to local and accidental fluctuationof the imaging pixel value Tc can be reduced. As a result, since thevirtual image display luminance Ld controlled corresponding to thecorrection pixel value Tr is less likely to cause a contrast defectcaused by such a variation error of the imaging pixel value Tc, thereliability of the visibility securing effect can be enhanced.

Third Embodiment

A third embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 13, in S103 of a display control flowaccording to the third embodiment, S3103 a and S3103 b are executed.

First, in S3103 a, a single-pixel portion obtained by capturing an imageof a portion overlapping with a display region Ad is selected as aspecific pixel portion Pc in a camera image 33 shown in FIG. 14, limitedto an outside scenery 8 on a near side of at least one of a vanishingpoint Hp and a horizon line HI. At that time, in the third embodiment, afixed single-pixel portion set in advance as shown in FIG. 14 isselected as the specific pixel portion Pc. At that time, in the thirdembodiment, the imaging pixel value Tc of the single-pixel portionforming the selected specific pixel portion Pc is extracted for eachcolor and stored in a memory 54 b. The single-pixel portion as thespecific pixel portion Pc is fixed to, for example, a pixelcorresponding to the center of the display region Ad in the camera image33.

Next, as shown in FIG. 13, in S3103 b, the imaging pixel values Tcextracted in S3103 a multiple times and stored in the memory 54 b foreach color, the average pixel value Tcave to be a correction conversionsource is calculated for each color. At that time, the number of timesof use of the imaging pixel value Tc in the calculation of the averagepixel value Tcave is set to a value capable of reducing an error due toa local and accidental variation of the imaging pixel value Tc. For thatreason, while the number of times of extracting the imaging pixel valueTc in S3103 a becomes smaller than the number of times of using theimaging pixel value Tc in S3103 b from a start of the display controlflow in response to on-operation of a power switch 41 a, the displaycontrol flow returns to S101 without executing S3103 b and subsequentsteps, although illustration is omitted.

In the third embodiment, the process shifts from S103 described above toS3104. In S3104, the average pixel value Tcave for each color calculatedin S3103 b is converted into the correction pixel value Tr for eachcolor in accordance with the outside brightness Lo detected in S102. Theconversion at that time is executed according to the first embodiment.In other words, the correction pixel value Tr corresponding to theaverage pixel value Tcave calculated in S3103 b is determined for eachof the colors based on the correction data Dr corresponding to theoutside brightness Lo detected in S102.

In the third embodiment described above, the functional part forexecuting S3103 a of the HCU 54 corresponds to an extraction block, andthe functional part for executing the S3103 b of the HCU 54 correspondsto an averaging block. In addition, in the third embodiment, thefunctional part for executing S3104 of the HCU 54 corresponds to aconversion block.

As described above, in the third embodiment, the correction pixel valueTr is converted from the average pixel value Tcave calculated byextracting the imaging pixel values Tc of the specific pixel portion Pcwhich is a single-pixel portion of the camera image 33 a multiple timesand averaging the imaging pixel values Tc. According to the averagepixel value Tcave extracted multiple times, an error caused by the localand accidental variation in the imaging pixel value Tc can be reduced.As a result, since the virtual image display luminance Ld controlledcorresponding to the correction pixel value Tr is less likely to cause acontrast defect caused by such a variation error of the imaging pixelvalue Tc, the reliability of the visibility securing effect can beenhanced.

Fourth Embodiment

A fourth embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 15, in S103 of a display control flowaccording to the fourth embodiment, imaging pixel values Tc of therespective pixels of the multiple pixel portion forming a specific pixelportion Pc are compared with each other for each of the colors in S4103b subsequent to S103 a. As a result, in S4103 b, as shown in FIG. 16,the maximum imaging pixel value Tc of a maximum-value pixel portion Pdwhich gives the maximum imaging pixel value Tc for each of the colors isextracted. At that time, in the fourth embodiment, the extracted imagingpixel value Tc for each color is stored in a memory 54 b.

In S103 of the display control flow according to the fourth embodiment,the display control flow shifts from S4103 b to S4103 c as shown in FIG.15. In S4103 c, the imaging pixel values Tc of the maximum-value pixelportions Pcl extracted in S4103 b multiple times and stored in thememory 54 b are averaged for each color, so that the average pixel valueTcave to be a correction conversion source is calculated for each color.At that time, the number of times of use of the imaging pixel value Tcin the calculation of the average pixel value Tcave is set to a valuecapable of reducing an error due to a local and accidental variation ofthe imaging pixel value Tc. For that reason, while the number of timesof extracting the imaging pixel value Tc in S4103 b becomes smaller thanthe number of times of using the imaging pixel value Tc in S4103 c froma start of the display control flow in response to on-operation of apower switch 41 a, the display control flow returns to S101 withoutexecuting S4103 c and subsequent steps, although illustration isomitted.

In the fourth embodiment, the process shifts from S103 to S4104. InS4104, the average pixel value Tcave for each color calculated in S4103c is converted into the correction pixel value Tr for each color inaccordance with the outside brightness Lo detected in S102. Theconversion at that time is executed according to the first embodiment.In other words, the correction pixel value Tr corresponding to theaverage pixel value Tcave calculated in S4103 c is determined for eachof the colors based on the correction data Dr corresponding to theoutside brightness La detected in S102.

In the fourth embodiment described above, the functional part forexecuting S4103 b of the HCU 54 corresponds to an extraction block, andthe functional part for executing the S4103 c of the HCU 54 correspondsto an averaging block. In addition, in the fourth embodiment, thefunctional part for executing the S4104 of the HCU 54 corresponds to aconversion block.

As described above, in the fourth embodiment, the imaging pixel value Tcof the specific pixel portion Pc which is the multiple pixel portion inthe camera image 33 is compared with each other to extract the imagingpixel value Tc of the maximum-value pixel portion Pcl which gives themaximum imaging pixel value Tc. Therefore, the correction pixel value Tris converted from the average pixel value Tcave calculated by extractingthe imaging pixel values Tc of the maximum-value pixel portion Pclmultiple times and averaging the imaging pixel values Tc. According tothe average pixel value Tcave extracted multiple times, an error causedby the local and accidental variation in the imaging pixel value Tc canbe reduced. As a result, since the virtual image display luminance Ldcontrolled corresponding to the correction pixel value Tr is less likelyto cause a contrast defect caused by such a variation error of theimaging pixel value Tc, the reliability of the visibility securingeffect can be enhanced.

Fifth Embodiment

A fifth embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 17, in S103 of a display control flowaccording to the fifth embodiment, in S5103 b subsequent to S103 a, aspecific pixel portion Pc of the camera image 33 shown in FIG. 18 and adisplay region Ad shown in FIG. 19 are divided into multiple pixel areasPd corresponding to each other, At that time, in an example of FIGS. 18and 19, the specific pixel portion Pc and the display region Ad aredivided so that the pixel areas Pd are arranged two by two in verticaland horizontal directions with each of multiple pixel portionscontinuous in the vertical and horizontal directions as one pixel areaPd.

In S103 of the display control flow according to the fifth embodiment,the display control flow shifts from S5103 b to S5103 c as shown in FIG.17. In S5103 c, the imaging pixel value Tc of each pixel in the cameraimage 33 divided in S5103 c is averaged for each color of each pixelarea Pd, so that an average pixel value Tcave serving as the correctionconversion source is calculated for each color of each pixel area Pd.

In the fifth embodiment, the process shifts from S103 to S5104. InS5104, the average pixel value Tcave for each color of each pixel areaPd calculated in S5103 c is converted into the correction pixel value Trfor each color of each pixel area Pd in accordance with the outsidebrightness Lo detected in S102. The conversion at that time is executedaccording to the first embodiment. In other words, the correction pixelvalue Tr corresponding to the average pixel value Tcave calculated inS5103 c is determined for each of the colors of each pixel area Pd basedon the correction data Dr corresponding to the outside brightness Lodetected in S102.

Further, in the fifth embodiment, the process shifts from S5104 toS5105, so that the display pixel value Td of each pixel of each pixelarea Pd in the display image 56 is adjusted for each color inassociation with the correction pixel value Tr for each color of eachpixel area Pd converted in S5104, individually. The adjustment at thattime is executed according to the first embodiment. In other words, thedisplay pixel values Td corresponding to the correction pixel values Trof the pixel areas Pd converted in S5104 are determined for each of thecolors on the basis of a pixel value control data Dct stored in thememory 54 b. At that time, a light source luminance value Sd of a lightsource unit 51 b is maintained at a fixed value according to the firstembodiment. As a result, a virtual image display luminance Ld of thedisplay image 56 in each pixel area Pd follows the determined displaypixel value Td, whereby the virtual image display luminance Ld iscontrolled individually corresponding to the correction pixel value Trin each pixel area Pd converted in S5104. It should be noted that S5105is continued fora valid time of the correction, and when the valid timehas elapsed, the process returns to S101.

In the fifth embodiment described above, the functional part forexecuting S5103 b of the HCU 54 corresponds to a division block, and thefunctional portion for executing S5103 c of the HCU 54 corresponds to anaveraging block. In addition, in the fifth embodiment, the functionalpart for executing S5104 of the HCU 54 corresponds to a conversionblock, and the functional part for executing S5105 of the HCU 54corresponds to a display control block.

As described above, in the fifth embodiment, the correction pixel valueTr of each pixel area Pd is converted from the average pixel value Tcaveas the imaging pixel value Tc of each pixel area Pd divided into themultiple pixels in the specific pixel portion Pc of the camera image 33.According to the above configuration, in each pixel area Pd of thedisplay region Ad divided in correspondence with the camera image 33,the virtual image display luminance Ld corresponding to the correctionpixel value Tr accurately reflecting an actual outside brightness Lo canbe individually controlled to a value for reducing the contrast defect.Therefore, the effect of ensuring visibility itself can be improved.

Sixth Embodiment

A sixth embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 20, in S6105 of a display controlflow according to the sixth embodiment, a light source luminance valueSd of a light source unit 51 b is adjusted in association with acorrection pixel value Tr of a specific color among correction pixelvalues Tr for each color converted in S104. In S104 of the sixthembodiment, only the specific color is converted into the correctionpixel value Tr, and in S6105, the light source luminance value Sd may beadjusted so as to correspond to the converted correction pixel value Trof the specific color. In this example, the specific color is set inadvance to the color G in the sixth embodiment, but may be set inadvance to another color R or B.

Specifically, the light source luminance value Sd is expressed byExpression 2 below with the use of an initial setting value Sd0 of thelight source luminance value Sd set in advance in the light source unit51 b and the correction pixel value Tr of a specific color and themaximum value Trmax of the correction pixel value Tr. FIG. 21 is asolid-line graph illustrating a correlation between the initial settingvalue Sd0 and the light source luminance value Sd according toExpression 2, where a ratio Tr/Trmax between the correction pixel valueTr and the maximum value Trmax is 0.4. Therefore, in order to determinethe light source luminance value Sd based on such a correlation, in thesixth embodiment, luminance value control data Dcs according toExpression 2 is prepared in the form of a table as shown in FIG. 22, andis stored in advance in a memory 54 b. The luminance value control dataDcs may be prepared in the form of an arithmetic expression expressingExpression 2.

Sd=Sd0×Tr/Tr max  (Expression 2)

In this manner, in S6105, the light source luminance value Sdcorresponding to the correction pixel value Tr of the specific colorconverted in S104 is determined based on the luminance value controldata Dcs stored in the memory 54 b. At that time, in the sixthembodiment, the display pixel value Td according to the display unit 51a is maintained and set to a fixed value. Therefore, the virtual imagedisplay luminance Ld of the display image 56 is controlled correspondingto the correction pixel value Tr converted in S104 by following thedetermined light source luminance value Sd. It should be noted thatS6105 is continued for a valid time of the correction, and when thevalid time has elapsed, the process returns to S101.

In the sixth embodiment, the functional part for executing S6105 of theHCU 54 corresponds to a display control block.

As described above, in the sixth embodiment, the light source luminancevalue Sd is adjusted so as to correspond to the correction pixel valueTr which is converted from the imaging pixel value Tc of the specificpixel portion Pc and accurately reflects an actual outside brightnessLo. Therefore, in the display image 56, according to the virtual imagedisplay luminance Ld determined according to the light source luminancevalue Sd corresponding to the correction pixel value Tr, a contrastdefect that causes a decrease in visibility can be reduced.

Seventh Embodiment

A seventh embodiment of the present disclosure is a modification of thefirst embodiment. As shown in FIG. 23, in S7105 of a display controlflow according to the seventh embodiment, a display pixel value Td ofeach pixel for each of colors in the display image 56 is controlled soas to individually correspond to the correction pixel value Tr of eachcolor converted in S104, and also so as to correspond to targetweighting data two. At the same time, in S7105, the light sourceluminance value Sd of the light source unit 51 b is controlled so as tocorrespond to the correction pixel value Tr of a specific color amongthe correction pixel values Tr for each color converted in S104 and alsoso as to correspond to the target weighting data Dwo. In the seventhembodiment, the specific color is set in advance to the color G, but maybe set in advance to another color R or B.

Specifically, the target weighting data Dwo is a numerical value forweighting the correction on the display pixel value Td rather than thelight source luminance value Sd. Therefore, the target weighting dataDwo is set and stored in advance in the memory 54 b such that the valuefor weighting the display pixel value Td is larger than the value forweighting the light source luminance value Sd and a sum of those valuesis set to 1. For example, the target weighting data Dwo is set to 0.25or the like smaller than 0.5 in the case of the light source luminancevalue Sd, and to 0.75 or the like larger than 0.5 in the case of thedisplay pixel value Td.

The display pixel value Td for each color is represented by Expression 3below with the use of the target weighting data Dwo, the initial settingvalue Td0 of the display pixel value Td, and the correction pixel valueTr for each color and the maximum value Trmax of the correction pixelvalue Tr. FIG. 24A is a solid line graph illustrating the correlationbetween the initial setting value Td0 and the display pixel value Tdaccording to Expression 3, where a ratio Tr/Trmax between the correctionpixel value Tr and the maximum value Trmax is 0.4. Therefore, in orderto determine the display pixel value Td based on such a correlation, inthe seventh embodiment, a pixel value control data Dct according toExpression 3 is prepared in the form of a table as shown in FIG. 25A,and is stored in advance in the memory 54 b. The pixel value controldata Dct may be prepared in the form of an arithmetic expressionrepresenting Expression 3.

Td=Dwo×Td0×Tr/Tr max  (Expression 3)

On the other hand, the light source luminance value Sd is expressed byExpression 4 below with the use of the target weighting data Dwo, aninitial setting value Sd0 of the light source luminance value Sd set inadvance in the light source unit 51 b and the correction pixel value Trof a specific color and the maximum value Trmax of the correction pixelvalue Tr. FIG. 24B is a solid-line graph illustrating a correlationbetween the initial setting value Sd0 and the light source luminancevalue Sd according to Expression 4, where a ratio Tr/Trmax between thecorrection pixel value Tr and the maximum value Trmax is 0.4. Therefore,in order to determine the light source luminance value Sd based on sucha correlation, in the seventh embodiment, luminance value control dataDcs according to Expression 4 is prepared in the form of a table asshown in FIG. 25B, and is stored in advance in a memory 54 b. Theluminance value control data Dcs may be prepared in the form of anarithmetic expression expressing Expression 4.

Sd=Dwo×Sd0×Tr/Tr max  (Expression 4)

In the seventh embodiment, in S7105, the display pixel value Td for eachcolor corresponding to not only the correction pixel value Tr for eachcolor converted in S104 but also the target weighting data Dwo in thepixel value control data Dct is determined based on the pixel valuecontrol data Dct stored in the memory 54 b. At the same time, in S7105,the light source luminance value Sd corresponding to not only thecorrection pixel value Tr of the specific color converted in S104 butalso the target weighting data Dwo in the luminance value control dataDcs is determined based on the luminance value control data Dcs storedin the memory 54 b. As a result, the virtual image display luminance Ldof the display image 56 is controlled corresponding to the correctionpixel value Tr converted in S104 by following the determined displaypixel value Td and the determined light source luminance value Sd foreach of the colors. It should be noted that S7105 is continued foravalid time of the correction, and when the valid time has elapsed, theprocess returns to S101.

In the seventh embodiment, the functional part for executing S7105 ofthe HCU 54 corresponds to a display control block.

As described above, in the seventh embodiment, the display pixel valueTd and the light source luminance value Sd are adjusted so as tocorrespond to the correction pixel value Tr which is converted from theimaging pixel value Tc of the specific pixel portion Pc and accuratelyreflects an actual outside brightness Lo. At that time, according to thetarget weighting data Dwo to which those adjustment targets are made tocorrespond, the former, which is one of the display pixel value Td andthe light source luminance value Sd, is given a correction weight morethan that of the latter, which is the other. According to the aboveconfiguration, with the combination of one priority adjustment targetwith the other auxiliary adjustment target, the resolution of thevirtual image display luminance Ld can be finely set to reduce thecontrast defect, so that the reliability of the visibility securingeffect can be enhanced.

OTHER EMBODIMENTS

Although a plurality of embodiments of the present disclosure have beendescribed above, the present disclosure is not construed as beinglimited to these embodiments, and can be applied to various embodimentsand combinations within a scope without departing from the spirit of thepresent disclosure.

In Modification 1 relating to the first to seventh embodiments, inaddition to or instead of the HCU 54, at least a part of the displaycontrol flows may be realized functionally (that is, in a software-likemanner) by the cooperation of one or more types of an ECU forcontrolling other display elements of the vehicle 2 and the ECUs 31, 42.In Modification 2 relating to the first to seventh embodiments, at leasta part of the display control flow may be realized by hardware using oneor multiple ICs or the like, instead of the display control flow beingrealized functionally by using the HCU 54 or the like.

In Modification 3 relating to the first to seventh embodiments, thestorage of the display image 56 may be realized by a memory built in theHUD 50 or another display element of the vehicle 2, or by a cooperationof the built-in memory and the memory 54 b. In Modification 4 relatingto the first to seventh embodiments, at least one type of data among thedata Dr, Dct, Dwc, Dwo, and Dcs may be realized by a memory built in theHUD 50 or another display element of the vehicle 2, or by a cooperationof the built-in memory and the memory 54 b.

In Modification 5 relating to the first to seventh embodiments, forexample, a pixel portion that changes in accordance with a time, avehicle speed, or the like may be selected as the specific pixel portionPc. In Modifications 6 relating to the first, second, and fourth toseventh embodiments, a predetermined number of discontinuous pixelportions in the pixel portion continuous in the vertical and horizontaldirections may be selected as the specific pixel portion Pc or the pixelarea Pd.

In Modification 7 related to the first to seventh embodiments, a pixelportion of the camera image 33, which includes the vanishing point Hp inthe outside scenery 8 (that is, extending vertically), may be selectedas the specific pixel portion Pc. In Modification 8 relating to thefirst to seventh embodiments, a pixel portion of the camera image 33 inwhich a portion including the horizon line HI (that is, extendingvertically) in the outside scenery 8 is imaged may be selected as thespecific pixel portion Pc.

In Modification 9 relating to the first to seventh embodiments, a partor the whole of the display region Ad may be deviated from the imagingregion Ac of the outside camera 30 a. In Modification 9, the imagingregion Ac may be set in addition to the front of the vehicle compartment2 a. In Modification 10 relating to the first to seventh embodiments, apart or the whole of the display region Ad may be out of the detectionregion Al of the brightness sensor 40 a. In Modification 10, thedetection region Al may be set at a position other than the front of thevehicle compartment 2 a.

In Modification 11 relating to the first to seventh embodiments, asshown in FIG. 26, at least one of the outside cameras 30 a and thebrightness sensor 40 a may be provided exclusively for the HUD 50. FIG.25 shows Modification 11 in which both the outside camera 30 a and thebrightness sensor 40 a are provided exclusively for the HUD 50.

In Modification 12 relating to the first to seventh embodiments, asshown in FIG. 27, the imaging pixel value Tc may represent gradationvalues for the luminance (Y), the color difference (U) between Y and B,and the color difference (V) between Y and R. In other words, inModification 12, the imaging pixel value Tc of each pixel is generatedby the outside camera 30 a in a YUV data format, and the correction dataDr is prepared for each of Y, U, and V as shown in FIG. 28. Therefore,in the case of Modification 12, the first to seventh embodiments can berealized by replacing each color and the specific color are replacedwith each of Y, U, and V and a specific one of Y, U, and V (in anexample of FIG. 28).

In Modification 13 relating to the first to seventh embodiments,individual correction data Dr for each color may be stored in the memory54 b by making the correlation between the imaging pixel value Tc andthe correction pixel value Tr different for each color. In Modification14 relating to the third embodiment, a value obtained by averaging theimaging pixel values Tc of the multiple pixel portion may be extractedmultiple times in accordance with the first embodiment, and thecorrection pixel value Tr may be converted from the average pixel valueTcave obtained by further averaging the extracted values multiple times.In Modification 15 relating to the third embodiment, the imaging pixelvalue Tc of the most-pixel portion Pcm may be extracted multiple timesin accordance with the second embodiment, and the correction pixel valueTr may be converted from the average pixel value Tcave obtained byaveraging the extracted values multiple times.

In Modification 16 relating to the fifth to seventh embodiments, theconversion of the correction pixel value Tr may be performed from theimaging pixel value Tc of the most-pixel portion Pcm in each pixel areaPd or the specific pixel portion Pc in accordance with the secondembodiment. In Modification 17 relating to the fifth to seventhembodiments, the average pixel value Tcave obtained by averaging theimaging pixel values Tc of the single-pixel portions extracted multipletimes in each of the respective pixel areas Pd or the specific pixelportions Pc may be converted into the correction pixel value Tr inaccordance with the third embodiment. In Modification 18 relating to thefifth to seventh embodiments, the average pixel value Tcave obtained byaveraging the imaging pixel values Tc of the maximum-value pixelportions Pcl extracted multiple times in each of the respective pixelareas Pd or the specific pixel portions Pc may be converted into thecorrection pixel value Tr in accordance with the fourth embodiment.

In Modification 19 relating to the seventh embodiment, the targetweighting data Dwo may be reflected in the correction pixel value Tr foreach color in the correction data Dr, instead of being reflected inExpressions 3 and 4 in which the pixel value control data Dct and theluminance value control data Dcs respectively follow. In the case ofModification 19, a value obtained by multiplying the correction pixelvalue Tr for each color described in the first embodiment by the targetweighting data Dwo as the correction pixel value Tr corresponding to thedisplay pixel value Td is introduced into Expression 3 in which Dwo=1(in other words, same as Expression 1). In the case of Modification 19,a value obtained by multiplying the correction pixel value Tr of thespecific color described in the seventh embodiment by the targetweighting data Dwo as the correction pixel value Tr corresponding to thelight source luminance value Sd is introduced into Expression 4 in whichDwo=1 (in other words, same as Expression 2).

In Modification 20, the seventh embodiment may be implemented incombination with the fifth embodiment. In Modification 21 relating tothe seventh embodiment, the target weighting data Dwo for weighting thecorrection on the light source luminance value Sd rather than thedisplay pixel value Td may be adopted. In Modification 22 relating tothe first to fifth embodiments, a laser scanning type projector 51 maybe employed. In Modification 22, the projector 51 adjusts the laserlight intensities of the multiple colors in accordance with the displaypixel values Td controlled by the HCU 54 to form the display images 56.

1. A vehicle display device provided in a vehicle mounted with anoutside camera that acquires a camera image by imaging outside sceneryand a brightness sensor that detects an outside brightness of theoutside scenery, the vehicle display device configured to project adisplay image onto a projection member, which transmits the outsidescenery, to display the display image as a visible virtual image in avisual recognition region in a vehicle compartment, the vehicle displaydevice comprising: a head-up display that emits light to form thedisplay image; a memory that stores, as correction data, a correlationof a correction pixel value with respect to an imaging pixel value, thecorrection pixel value being converted from the imaging pixel valueforming the camera image by a correction according to the outsidebrightness; a conversion block that converts, based on the correctiondata stored in the memory, the imaging pixel value of a specific pixelportion captured on a near side of at least one of a vanishing point ora horizon line in the camera image acquired by the outside camera intothe correction pixel value in accordance with the outside brightnessdetected by the brightness sensor; and a display control block thatcontrols a virtual image display luminance of the display imagedisplayed by the head-up display in correspondence with the correctionpixel value converted from the imaging pixel value by the conversionblock.
 2. The vehicle display device according to claim 1, wherein thehead-up display displays the display image as the virtual image in adisplay region, and the display region is included in an imaging regionof the outside camera and a detection region of the brightness sensor.3. The vehicle display device according to claim 1, further comprisingan average block that calculates an average pixel value by averagingimaging pixel values of a multiple pixel portion as the specific pixelportion of the camera image acquired by the outside camera, wherein theconversion block converts the average pixel value calculated by theaveraging block into the correction pixel value.
 4. The vehicle displaydevice according to claim 1, further comprising an extraction block thatextracts the imaging pixel value of a most-pixel portion, in which thenumber of pixels is greatest given a same imaging pixel value or withina same range, by comparing imaging pixel values of a multiple pixelportion as the specific pixel portion in the camera image acquired bythe outside camera, wherein the conversion block converts the imagingpixel value of the most-pixel portion extracted by the extraction blockinto the correction pixel value.
 5. The vehicle display device accordingto claim 1, further comprising: an extraction block that extracts theimaging pixel value of a single-pixel portion as the specific pixelportion from the camera image acquired by the outside camera; and anaveraging block that calculates an average pixel value by averagingimaging pixel values of multiple single pixel portions extracted over aplurality of times by the extraction block; wherein the conversion blockconverts the average pixel value calculated by the average block intothe correction pixel value.
 6. The vehicle display device according toclaim 1, further comprising: an extraction block that extracts theimaging pixel value of a maximum-value pixel portion having a largestimaging pixel value by comparing imaging pixel values of a multiplepixel portion as the specific pixel portion in the camera image acquiredby the outside camera; and an averaging block that calculates an averagepixel value by averaging imaging pixel values of multiple largest-valuepixel portions extracted over a plurality of times by the extractionblock, wherein the conversion block converts the average pixel valuecalculated by the average block into the correction pixel value.
 7. Thevehicle display device according to claim 1, further comprising: adivision block that divides the specific pixel portion of the cameraimage acquired by the outside camera and a display region in which thedisplay image is displayed as the virtual image by the head-up displayinto a plurality of corresponding pixel areas, wherein the conversionblock converts imaging pixel values of the pixel areas of the specificpixel portion divided by the division block into correspondingcorrection pixel values, and the display control block controls thevirtual image display luminance of each of the pixel areas of thedisplay image displayed by the head-up display in association with thecorresponding correction pixel value of each pixel area of the specificpixel portion converted from the imaging pixel value by the conversionblock.
 8. The vehicle display device according to claim 1, wherein thedisplay control block adjusts a display pixel value of the display imageformed by the head-up display in correspondence with the correctionpixel value converted from the imaging pixel value of the specific pixelportion by the conversion block.
 9. The vehicle display device accordingto claim 1, wherein the display control block adjusts a light sourceluminance value for causing the head-up display to emit the light of thedisplay image in correspondence with the correction pixel valueconverted from the imaging pixel value of the specific pixel portion bythe conversion block.
 10. The vehicle display device according to claim1, wherein the memory stores target weighting data for weightingcorrection of a display pixel value of the display image formed by thehead-up display or a light source luminance value for causing thehead-up display to emit the light of the display image more than that ofthe other, and the display control block adjusts the display pixel valueand the light source luminance value in correspondence with thecorrection pixel value converted from the imaging pixel value of thespecific pixel portion by the conversion block and in correspondencewith the target weighting data stored in the memory.
 11. A vehicledisplay system for a vehicle, comprising: an outside camera configuredto acquire a camera image by imaging outside scenery; a brightnesssensor that detects an outside brightness of the outside scenery; ahead-up display configured to emit light to project a display image ontoa light-transmissive projection member of the vehicle, the projecteddisplay image being displayed as a visible virtual image; a memory thatstores, as correction data, a correlation of a correction pixel valuewith respect to an imaging pixel value forming the camera image, thecorrection pixel value being converted from the imaging pixel value by acorrection according to the outside brightness; and one or moreprocessors collectively programmed to: convert, based on the correctiondata stored in the memory, the imaging pixel value of a specific pixelportion captured on a near side of at least one of a vanishing point ora horizon line in the camera image acquired by the outside camera intothe correction pixel value in accordance with the outside brightnessdetected by the brightness sensor, and control a virtual image displayluminance of the display image displayed by the head-up display incorrespondence with the correction pixel value converted from theimaging pixel value by the conversion block.